In vivo electron spin resonance analysis of nitroxide radicals injected into a rat by a flexible surface-coil-type resonator as an endoscope- or a stethoscope-like device

The flexible surface-coil-type resonator (FSCR) operating in a 700 MHz microwave electron spin resonance (ESR) system was applied to measure the nitroxide radicals at a specific area in rats. The FSCR was composed of a single-turn coil with a diameter of 5 mm and two flexible coaxial lines of 450 mm in length. For an endoscope-like application, the FSCR was inserted into the rectum of the rat and sequential changes in the ESR signals of the intravenously injected nitroxide radical (4-hydroxy-2,2,6,6-tetramethyl-piperidine-1-oxyl; TEMPOL or 3-carbamoyl-2,2,5,5-tetramethyl-pyrrolidine-1-yloxy; carbamoyl-PROXYL) were measured. The ESR signal intensity of the nitroxide decreased according to first-order kinetics. For a stethoscope-like application, the FSCR was placed at several sites on the abdominal skin of the rats receiving a subcutaneous injection of carbamoyl-PROXYL, and diffusion and/or metabolism of the radical in the skin was observed.     

In vivo 300 MHz longitudinally detected ESR-CT imaging in the head of a rat treated with a nitroxide radical

In vivo longitudinally detected ESR (LODESR)-CT system operating at 300 MHz was developed, based on the combination of a bridged loop-gap resonator and a pair of saddle-type pickup coils (STPCs). The sensitivity distribution of the STPCs was simulated on the basis of a magnetic dipole model. A LODESR-CT image of a phantom (a physiological saline solution of a nitroxide radical) was satisfactorily corrected by using the simulation result. LODESR-CT images of the head of a rats, in which nitroxide radical was injected intraperitonally, were also obtained through the correction in the same manner. This is the first in vivo CT (i.e. three-dimensional imaging) study with a 300 MHz ESR.     

Use of spin-traps during warm ischemia-reperfusion in rat liver: comparative effect on energetic metabolism studied using31P nuclear magnetic resonance

Detection of free radicals by electron spin resonance (ESR) proves the involvement of reactive oxygen species (ROS) in reperfused organ injuries. Spin-traps are known to ameliorate hemodynamic parameters in an isolated postischemic heart. The effects of 5 mmol/L DMPO (5,5-dimethyl-1-pyrroline-N-oxide) or DEPMPO (5-(diethylphosphoryl)-5-methyl-1-pyrrolineN-oxide) on intracellular pH (pH_in) and ATP level were evaluated by³¹P nuclear magnetic resonance on isolated rat liver submitted to 1 hour of warm ischemia and reperfusion. At the end of the reperfusion period, during which pH_in recovered to its initial value (7.16±0.03) in all groups, the ATP recovery level (expressed in percentage of initial value) was similar in controls and DEPMPO (60%±5%,n=6 and 54%±4%,n=6, respectively), but only 37%±1% in DMPO-treated livers (n=6) (p<0.05 versus controls andp<0.05 versus DEPMPO). Oxidative phosphorylation was not affected by an addition of nitrones on isolated mitochondria extracted from livers not submitted to ischemia-reperfusion. In contrast, mitochondria extracted at the end of the ischemia-reperfusion showed an impairment in the phosphorylation parameters, particularly in the presence of DMPO. Mass spectrum of ischemic liver perchloric acid extracts evidenced probable catabolites in treated groups. The differences in the effect of the two nitrones on energetic metabolism may be explained by the production of deleterious catabolites by DMPO as compared to DEPMPO. Even though a specific radical scavenging effect could be operative in the liver, our results indicate that catabolic effects were predominant. The absence of deleterious effects of DEPMPO in contrast to DMPO on the liver energetic metabolism was evidenced, allowing the use of DEPMPO for ESR detection.     

Feasibility of in vivo three-dimensional T<Stack><Subscript>2</Subscript><Superscript>*</Superscript></Stack> mapping using dicarboxy-PROXYL and CW-EPR-based single-point imaging

Objectives

The aim of this study was to demonstrate the feasibility of in vivo three-dimensional (3D) relaxation time T ₂ ^* mapping of a dicarboxy-PROXYL radical using continuous-wave electron paramagnetic resonance (CW-EPR) imaging.

Materials and methods

Isotopically substituted dicarboxy-PROXYL radicals, 3,4-dicarboxy-2,2,5,5-tetra(²H₃)methylpyrrolidin-(3,4-²H₂)-(1-¹⁵N)-1-oxyl (²H,¹⁵N-DCP) and 3,4-dicarboxy-2,2,5,5-tetra(²H₃)methylpyrrolidin-(3,4-²H₂)-1-oxyl (²H-DCP), were used in the study. A clonogenic cell survival assay was performed with the ²H-DCP radical using squamous cell carcinoma (SCC VII) cells. The time course of EPR signal intensities of intravenously injected ²H,¹⁵N-DCP and ²H-DCP radicals were determined in tumor-bearing hind legs of mice (C3H/HeJ, male, n = 5). CW-EPR-based single-point imaging (SPI) was performed for 3D T ₂ ^* mapping.

Results

²H-DCP radical did not exhibit cytotoxicity at concentrations below 10 mM. The in vivo half-life of ²H,¹⁵N-DCP in tumor tissues was 24.7 ± 2.9 min (mean ± standard deviation [SD], n = 5). The in vivo time course of the EPR signal intensity of the ²H,¹⁵N-DCP radical showed a plateau of 10.2 ± 1.2 min (mean ± SD) where the EPR signal intensity remained at more than 90% of the maximum intensity. During the plateau, in vivo 3D T ₂ ^* maps with ²H,¹⁵N-DCP were obtained from tumor-bearing hind legs, with a total acquisition time of 7.5 min.

Conclusion

EPR signals of ²H,¹⁵N-DCP persisted long enough after bolus intravenous injection to conduct in vivo 3D T ₂ ^* mapping with CW-EPR-based SPI.

     

Progress in the development of high-power millimeter- and submillimeter wave gyrotrons and of free electron masers

Contents At present, high power gyrotron oscillators are mainly used as generators for electron cyclotron resonance heating (ECRH) and diagnostics of magnetically confined plasmas for generation of energy by controlled thermonuclear fusion. 140 GHz gyrotrons with output powerP _out =0.58 MW in the Gaussian free space TEM₀₀ mode with pulse length up to =2.0 s and efficiency =34% are commercially available. High order rotating TE-modes (e.g. TE_22,6 at 140 GHz) are used as working modes in the cavities of these tubes. For plasma diagnostics higher frequencies are required. Therefore, gyrotron oscillators are designed for operation either at the second harmonic of the electron cyclotron frequency or at the fundamental cyclotron frequency with special pulsed high-field solenoids.P _out =40 kW with =40 s at =4% at frequencies up to 650 GHz have been achieved. In the case of gyrotron oscillators only slow frequency step tuning is possible by variation of the magnetic field (change of operating cavity mode). Fast and continuous frequency tuning by variation of the beam acceleration voltage is feasible for free electron masers (FEM). Record output parameters are:P _out =2GW, =20 ns, =13% at 140 GHz (LLNL) andP _out =15 kW, =20 s, =5% in the range from 120 to 900 GHz (UCSB).

---

Fortschritte bei der Entwicklung von Hochleistungs-Millimeter- und Submillimeter-Wellen Gyrotrons und Frei-Elektronen-Masern

Übersicht Hochleistungs-Gyrotronoszillatoren werden derzeit vorwiegend als Generatoren für die Elektronen-Zyklotron-Resonanz-Heizung (ECRH) und Diagnostik von magnetisch eingeschlossenen Plasmen zur Erforschung der Energiegewinnung durch kontrollierte Kernfusion eingesetzt. 140 GHz Gyrotrons mit einer Ausgangsleistung vonP _out =0.58 MW in der Gaußschen Freiraumgrundmode TEM₀₀ bei Pulslängen bis zu =2.0 s und Wirkungsgraden =34% sind kommerziell erhältlich. Als Arbeitsmoden im Röhrenresonator dienen dabei hohe, rotierende TE-Moden (z. B. TE_22,6 bei 140 GHz). Zur Plasmadiagnostik werden höhere Frequenzen benötigt. Daher arbeiten die dazu vorgesehenen Gyroronoszillatoren entweder bei der 2. Harmonischen der Elektronen-Zyklotronfrequenz oder bei der Grundfrequenz mit speziellen gepulsten Hochfeld-Magneten. Bisher wurde bei Frequenzen bis zu 650 GHz eine HF-Ausgangsleistung vonP _out =40 kW mit =40 s und =4% erreicht. Die Ausgangsfrequenz von Gyrotronoszillatoren ist dabei nur langsam und stufenweise durch Veränderung des Magnetfeldes durchstimmbar (Übergang zu anderen Arbeitswellentypen im Resonator). Schnelle und kontinuierliche Frequenzdurchstimmbarkeit (über die Beschleunigungsspannung) ist beim Frei-Elektronen-Maser (FEM) gegeben. Rekordausgangsparameter sind hier:P _out =2 GW, =20 ns, =13% bei 140 GHz (LLNL) undP _out =15 kW, =20 s, =5% im Bereich von 120 bis 900 GHz (UCSB).

     

Cationic Surface Segregation in Donor-Doped SrTiO3 Under Oxidizing Conditions

The influence of high temperature oxygen annealing on (100) oriented donor-doped SrTiO₃ single crystals was studied. Crystalline precipitates were found on the optical scale on surfaces of lanthanum-doped as well as niobium-doped specimens with donor concentrations above 0.5 at.%. The amount of the secondary phase increases with the doping level, oxidation temperature and oxidation time. EDX analyses of the crystallites reveal a SrO_x composition.The formation of the observed secondary phase is discussed by means of the defect re-equilibration of the cation sub-lattice. In view of the point defect model for donor-doped perovskites, n-conducting SrTiO₃ changes its compensation mechanism during an oxidation treatment from electronic compensation (N _D = n) to self-compensation (N _D = 2[V _Sr]) by forming cation vacancies. Due to the favored Schottky-type disorder in perovskites, the formation of strontium vacancies is accompanied by a release of strontium from the regular lattice. Since the excess strontium is found to be situated at the surface in form of SrO-rich precipitates only, we propose the formation of strontium vacancies via a surface defect reaction and the chemical diffusion of strontium vacancies from the surface into the crystal as the most probable re-equilibration mechanism for the oxidation treatment of single crystals.The introduced mechanism is in contrast to an established model which proposes the formation of Ruddlesden-Popper intergrowth phases SrO·(SrTiO₃)_n in the interior of the crystal.     

Versatile coil design and positioning of transverse-field RF surface coils for clinical 1.5-T MRI applications

Clinical MRI/MRS applications require radio frequency (RF) surface coils positioned at an arbitrary angle with respect to B₀. In these experimental conditions the standard circular loop (CL) coil, producing an axial RF field, shows a large signal loss in the central region of interest (ROI). We demonstrate that transverse-field figure-of-eight (FO8) RF surface coils design are not subject to the same amount of signal loss in the central ROI as loop coils when their orientations are changed. The 1.5-T CL and FO8 prototypes (diameter = 10 cm) were built on Plexiglas using copper strips (width = 4 mm, thickness = 100 m). The two linear elements of the FO8 coil were 1 cm apart. Axial spoiled gradient echo (SPGR) images of a phantom containing doped water were acquired with the coil plane at =0°, 45°, and 90°. As increases, the CL images show, in the central ROI, a signal that decreases from a maximum value to zero. Whereas the FO8 images show, in the same ROI, a signal that varies little from the maximum value (20%). Optimized FO8 coils can be oriented with the coil plane positioned along any direction with respect to B₀ without significant signal loss. Transverse RF coil design should be useful for clinical MRS studies and also for parallel imaging techniques where versatile RF coils disposed along arbitrary directions are required.     

Dielectric Characteristics and Tunability of Barium Stannate Titanate Ceramics

Ba(Ti_{1 –x} Sn _x )O₃ solid solutions were prepared by a solid state reaction method, and their dielectric and tunable characteristics were investigated together with the microstructures and diffused phase transition behaviors. The dielectric relaxation behaviors were observed and became stronger with increasing x.The obvious field dependence of the present system was observed with high dielectric constant and low loss at relatively lower DC electric field. The excellent tunable dielectric characteristics were achieved for x= 0.15 at room temperature: tunability 56%, tan 0.003 at 10 kHz under 7.6 kV/cm, indicating that it is a promising candidate for electric-field tunable dielectrics working at room temperature.     

A quasi analytical procedure for determining the optimum commutation angles of PWM converters

Contents A method for calculating the optimum commutation times for PWM converters is proposed. The method is mainly analytical and leads to a simple, fast calculation procedure. The time behaviour of any variable, electrical or non electrical, which is considered to be the most characteristic of the behaviour of the system, can be optimized. The validity of the analytical approach is subject to some hypotheses which are often verified in practice. The computation power required by the method is so limited that, in the majority of cases, a minicomputer can be used.

---

Quasi analytische Bestimmung der optimalen Steuerwinkel für pulsbreitenmodulierte Frequenzumrichter

Übersicht Man beschreibt ein meist analytisches Verfahren für die Berechnung der optimalen Steuerwinkel für pulsbreiten-modulierte Frequenzumrichter. Durch dieses Verfahren wird es möglich, den Zeitverlauf der bedeutendsten elektrischen und nichtelektrischen Größen des Systems zu optimieren. Das Rechnungsverfahren beruht auf meistens erfüllten Annahmen; auf Grund seiner einfachen und schnellen Durchführung braucht man in den meisten Fällen nur Minicomputer zum Zweck.

---

List of symbols fundamental frequency - x(t) modulated wave (input wave) - y(t) variable to be optimized (output wave) - f ^*() transfer function - f ^*() f ^*() amplitude - ^*() f ^*() phase - f(n) f ^*() evaluated only in correspondence with () _f integer multipliers - a _n x(t) Fourier coefficients relative to the terms cos (n _f t) - b _n x(t) Fourier coefficients relative to the terms sin (n _f t) - a _n ,b _n asa _n ,b _n , but relative toy(t) - y _d (t) required output wave-form - a _d (n), b _d (n) y _d (t) Fourier coefficients - y _s (t) deviation function (defined asy(t)–y _d (t)) - a _s (n), b _s (n) y _s (t) Fourier coefficients - ^* rms value ofy _s - as ^* except for some constants - _i commutation angles - m ₁ commutations number in the first half of the period - m number of independent commutations in the period - _ij , _ij x _ij auxiliary variables dependent on the _i - V _k numerical values relative to the links imposed onx(t)'s,y(t)'s harmonics - peak values ofy(t) andx(t) harmonic of ordern - Y _n ,X _n rms values of ordern harmonics ofy(t) andx(t) - _j Lagrange multipliers - z number of constraints relative tox(t)'s harmonics Research supported by Italian Research Council (C.N.R.)     

T2 Relaxation time study of the pig renal allografts

A previous study showed the possibility of the dependence of theT ₂ maps measured by Siemens Magnetom MR imager 1.5 T on the viability of the cadaveric kidney. For theT ₂ relaxometry study the pig model was used. Ten pig renal allografts were examined during 68 h after removal. Significant differences were found in the change of the initialT ₂ ⁱⁿⁱ values in the histogram within the first 20 h [₁=T ₂ ⁱⁿⁱ (2)–T ₂ ⁱⁿⁱ (20)] or 8 h [₂=T ₂ ⁱⁿⁱ (2)–T ₂ ⁿⁱ (8)] after removal between the groups of the damaged kidneys (₁=20.2±6.8 ms, ₂=19.4±3.0) and the kidneys without apparent damage (₁=9.4±8.5 ms, ₂=5.4±5.8).     

A proposed theory of local induced voltage velometry of conductive fluids

Contents The paper deals with the problem of determining velocity profiles in electrically conductive fluids. The fluid flows in a round nonconductive tube and is submitted to the action of purely transversal multipolar inhomogeneous fields which induce voltages at the insulating wall. These voltages are proportional to certain surface intergrals of the flow velocity, weighted with some power of the radial coordinate. The inverse problem consists in deriving the velocity profile from these integrals; the problem is ill-conditioned and the best solution was obtained as a Fourier-Legendre series. The coefficients of the Fourier-Legendre series can also be determined by direct measurements of induced voltages. The magnetic fields suitable for this latter measurement are multipolar inhomogeneous fields shifted with respect to the tube axis.

---

Versuch einer Theorie der lokalen Geschwindigkeitsmessung leitender Fluide mit induktivem Verfahren

Übersicht Die Arbeit ist dem Problem der Bestimmung von Geschwindigkeitsprofilen bei elektrisch leitenden Fluiden gewidmet. Das Fluid strömt in cinem nichtleitenden Rohr von rundem Querschnitt und ist durch nichthomogene mehrpolige, rein transversale Magnetfelder bewirkt, die elektrische Spannungen an der isolierenden Wand induzieren. Diese Spannungen sind gewissen Flächenintegralen der Flußgeschwindigkeit proportional, in die eine Potenz der Radialkoordinate als Gewichtsfunktion eingeht. Das inverse Problem ist, das Geschwindigkeitsprofil aus diesen Integralen auszusonderen; das Problem ist schlecht lösbar und die beste Lösung wurde in der Form einer Fourier-Legendreschen Reihe gefunden. Die Koeffizienten der Fourier-Legendreschen Reihe kann man auch durch direkte Messung von induzierten Spannungen bestimmen. Die Magnetfelder, die sich zu dieser Messung eignen, sind mehrpolige inhomogene Felder, deren Achse gegen die Rohrachse versetzt ist.

---

List of Symbols nabla operator - V electric scalar potential - B vector of magnetic induction - v local fluid velocity - J _n normal component of the current density vector - r, polar coordinates - n multipole order - A _n strength of a multipole field of ordern - V _m magnetic scalar potential - v _z axial velocity component (flow velocity) - U,U _AB open circuit voltage at the electrodes - I _n ,I _n ^* axial moments of a velocity profile - a tube radius - =r/a normalized radial coordinate - u=² square of the normalized radial coordinate - a _k coefficient in polynomial expansion - N number of coefficients used in an expansion and number of multipolar fields used in a measurement - polynomials inn - mean flow velocity absolute error in flow velocity - v _z absolute error in flow velocity - x=2u–1 shifted square of normalized radial coordinate - b _k coefficient in Legendre polynomial expansion - P _k (_X) Legendre polynomial - angle between two electrodes - b radius of a pole tip measured from the center of fiedl symmetry     

Quantitative assessment of regional myocardial function in a rat model of myocardial infarction using tagged MRI

We characterized global and regional left ventricular (LV) function during post myocardium infarction (MI) remodeling in rats, which has been incompletely described by previous MRI studies. To assess regional wall motion, four groups of infarcted animals corresponding to 1–2, 3–4, 6–8 and 9–12 weeks post-MI respectively were imaged using a fast gradient echo sequence with a 2D spatial modulation of magnetization (SPAMM) tagging preparation. An additional group was serially imaged (1–2 and 6–7 weeks post-MI) to assess the global function. Regional and global functional parameters of infarcted rats were compared to non-infarcted normal rats. Compared to normal rats, a decrease in ejection fraction (70 ±7 vs. 40 ± 8%, p<0.05) was observed in rats with MI. Maximal and minimal principal stretches (₁, ₂) and strains (E₁, E₂), principal angle () and displacement varied regionally in normal rats but deviated significantly from the normal values in rats with MI particularly in the infarcted and adjacent zones. Not only was strain magnitude reduced segmentally post-MI, but strain direction became more circumferentially oriented, particularly in rats with larger infarctions. We report the first regional myocardial strain values in normal and infarcted rats. These results parallel findings in humans, and provide a unique tool to examine regional mechanical influences on the remodeling process.     

Evaluation of adipose tissue distribution in obese fa/fa Zucker rats by in vivo MR imaging: effects of peroxisome proliferator-activated receptor agonists

High-resolution MRI of obese (fa/fa) Zucker rats was investigated to characterize and assess in vivo adipose tissue distribution. Thirty animals were gavaged with a placebo, a PPAR activator (pioglitazone), or a dual PPAR activator (LM 4156). At day 15, T₁-weighted images were acquired in vivo using a 2TMRI system with a high in-plane spatial resolution (254 m). Fat volumes of selected territories were measured by image segmentation, and the retroperitoneal fat was weighed post-mortem. Body-weight gain was significant with pioglitazone (101.8±5.9 g, p<0.01 vs. placebo). The good quality of MR images allowed the delimitation and quantification of different fat territories. In response to pioglitazone, the retroperitoneal fat was more important compared to placebo (+23%, p<0.01) while subcutaneous fat was not different. No significant effects were observed with LM 4156. In vivo measurements of fat volumes were strongly correlated with ex vivo tissue weights (r=0.91). High-resolution MRI provides an in vivo measurement of adipose tissue distribution in obese Zucker rats. Specific fat depots of regions that were particularly involved in drug response were determined in vivo. Fat remodeling was observed with pioglitazone but not with a dual PPAR activator (LM 4156).     

Short circuit losses in three phase arrangements with nonmagnetic enclosure

Contents In this paper analytic relations are developed for the calculation of the shell losses in three phase arrangements with nonmagnetic enclosure, for the steady state and the short circuit conditions. The phase conductors are taken as filamentary. The losses result as Fourier series ofn terms. Parametric investigations showed that a restriction on two terms gives results of great accuracy for the steady state losses. The analytic relations for the short circuit losses calculation are cumbersome. These losses can be calculated from the steady state losses, that are given from simpler relations, by an appropriate coefficient given here from the relevant curves.

---

Kurzschlußverluste in Dreileiterkapselungen mit unmagnetischem Mantel

Ubersicht In dieser Arbeit werden analytische Beziehungen zur Berechnung der Mantelverluste für Dreileiterkapselungen mit unmagnetischem Mantel im stationären Betrieb und im Kurzschlußfall entwickelt. Die Innenleiter werden als Linienleiter betrachtet (Leiterradiusr=0). Die Verluste erhält man als Fourier-Reihen mitn Gliedern. Durch Parameteruntersuchungen der Verluste im stationären Betrieb ergibt sich, daß die ersten beiden Glieder für die erforderlichen Genauigkeit ausreichend sind. Die analytischen Beziehungen für dieKurzschlußverlust-berechnung sind umfangreich. Diese Verluste können aber aus den Verlusten im stationären Betrieb mit Hilfe eines geeigneten Faktors berechnet werden, der aus Diagrammen entnommen werden kann.

---

List of symbols A _M vector potential at the shell - A _n ,B _n Fourier coefficients - d _M shell thickness - i instantaneous current - I _cc RMS value of the short-circuit current - I _th thermal equivalent short-time current - K _M current line density at the shell - K _Mth thermal equivalent short-time current line density - m conductor distance from the arrangement center - n terms of Fourier series - p abbreviation, eq. (10) - P _cc short-circuit shell losses per unit length - P _M steady-state shell losses per unit length - P _M 0 reference shell losses per unit length, eq. (13) - q abbreviation, eq. (A. 2a) - Q thermal losses per unit length - R resistive component of the short-circuit power system impedance - R{imM} mean shell radius - R _s shell resistance per unit length - t time - T _cc short-circuit duration - X inductive component of the short-circuit power system impedance - angle; describes the instantaneous values of voltages at the moment of fault appearance - angle of the short-circuit power system impedance, eq. (2) - skin depth - factor for the computation of short-circuit current, eq. (26) - _M shell conductivity - _M surface conductance of the shell _M = _M d _M - eigenvalue (=1/) - ₀ vacuum permeability ( ₀=4×10^–7H/m) - time constant, eq. (3) - circular system frequency     

Short-circuit electromagnetic forces in three phase gas insulated systems with steel enclosure

Contents In this paper, the short-circuit forces acting on the phase-conductors of arrangements with 3-phase steel enclosure, are examined. In the case of tubular conductors the forces result from the vector potentials calculated in the different arrangement areas. The potentials result as Fourier series ofn terms; their coefficients are determined from the numerical solution of a 10×n algebraic equations system. But in the case of filamentary conductors the corresponding system of equations consists of two independent systems, 4×n equations each, that can be analytically solved and lead to simpler relations for the forces.Parametric investigations showed that, for the praxis arrangements, the influence of the conductor radius on forces is very small and consequently the conductors may be considered as filamentary.The influence of the relative permeability, the conductivity and the thickness of the shell on the electromagnetic forces has also been examined.

---

Elektromagnetische Kurzschlußkräfte in dreiphasig gekapselten Systemen mit Mantel aus Stahl

Übersicht In dieser Arbeit werden die elektromagnetischen Kurzschlußkräfte untersucht, welche auf die drei Außenleiter in symmetrischen Anordnungen im gemeinsamen Mantel aus Stahl angreifen. Die Kräfte ergeben sich für den Fall von Rohrleitern aus den Vektorpotentialen in den verschiedenen Bereichen der Anordnung. Die Vektorpotentiale erhält man als Fourier-Reihen mitn Gliedern, mit Koeffizienten aus der numerischen Lösung eines Systems von 10×n algebraischen Gleichungen. Bei Linienleitern besteht aber das entsprechende System aus zwei Systemen von 4×n Gleichungen, deren analytische Lösung auf einfachere Ausdrücke für die Kräfte führt.Parameter-Untersuchungen haben gezeigt, daß der Leiterradius vernachlässigt werden darf und somit die Leiter als Linienleiter angeschen werden dürfen. Untersucht wird auch der Einfluß der magnetischen Permeabilität, der elektrischen Leitfähigkeit und der Wanddicke des Mantels auf elektromagnetische Kräfte.

---

List of symbols A vector potential - a _n ,b _n ,A _n ,A _n ,B _n ,B _n ,C _n ,C _n ,D _n ,D _n ,C _1n ,C _1n Fourier coefficients - B magnetic induction - d thickness (d _c for the conductor,d _M for the shell) - F _ax ,F _ay electromagnetic forces on conductora inx andy directions, as shown in Fig. 1 - f related toF ₀ electromagnetic force,F ₀ according to eqn. (20) - f _st related toF ₀ peak electromagnetic force - H magnetic field intensity - I _cc RMS value of the short-circuit current - K current line density - conductivity ( _c for the conductor, _M for the shell) - _c surface conductivity of the conductor ( _c = _c d _d - skin depth - ₀ vacuum permeability - shell permeability - _r shell relative permeability      

Surface Structure of Oxygen Annealed Donor Doped SrTiO3(100) Single Crystals Studied with Spectroscopic Electron Microscopy

Heating 5at.% (on A-site) La-doped SrTiO₃(100) single crystals in an ambient atmosphere at 1300°C for 120 h results in the formation of insulating islands on top of the surface with typical dimensions of up to 50 m. The islands and the surface between them were investigated by spectroscopic Metastable Impact Electron Emission Microscopy (specMIEEM) and Photoelectron Emission Microscopy in order to determine its electronic and geometric structure.The comparison of specMIEEM results with MIES (Metastable Impact Electron Spectroscopy) spectra from stoichiometric SrO shows that the insulating islands, which most likely consist of SrO, are at least partly covered by another species, probably SrO₂. All these islands are surrounded by 2–3 m wide haloes. The electronic structure of these haloes is quite different from that of SrO and SrTiO₃ but similar to the electronic structure of TiO₂ or Ti₂O₃. It is suggested that the depletion of SrO from Ruddlesden-Popper (Sr _{n + 1}Ti _n O_{3n + 1}) phases results in the formation of SrO islands.     

Zur Leistungsberechnung aus asynchron abgetasteten Strom- und Spannungssignalen

Übersicht Bei der digitalen Leistungsmessung wird die Leistung durch Mittelung über viele Produkte aus Momentanwerten von Strom und Spannung bestimmt. Strom- und Spannungsmeßwerte liegen hierbei in Form von äquidistanten Sequenzen von Abtastwerten vor, wobei im allgemeinen Fall die Abtastzeitpunkte weder untereinander noch mit dem Rechenvorgang synchronisiert sind. — Es wird ein Rechenverfahren angegeben, um die in diesem Fall zu erwartenden Meßfehler zu ermitteln. Wie sich zeigt, tritt neben beständigen Meßfehlern auch ein Meßwerttanzen auf, das bei bestimmten Zahlenrelationen der Abtast- und Rechenintervalle resonanzartig hohe Werte annimmt und auch durch Mittelung über beliebig viele Strom-Spannungsprodukte nicht unterdrückt werden kann.

---

On the computation of real power from asynchronous samples of current and voltagePart 1: Method of analysis

Contents Digital measurement of power means averaging many products of instant values of voltage and current. The measuring values of voltage and current consist of equidistant sequences of digitized samples, which — in the general case — are not mutually synchronized nor synchronized with the computation process. — A method is derived for calculating the measuring deviations to be expected in that general case. It is shown that beside stationary deviations a jumping of measurands appears which will attain high values at special numerical relations between sampling- and computing intervals and cannot be subdued by extending the average over any number of products.

---

Liste der verwendeten Formelzeichen P Wirkleistung - P, P Erwartungswert u. Schwankungsbereich des Meßergebnisses - Q Blindleistung - S Scheinleistung - Alterswert (Zeitdifferenz zwischen Abtastung und Produktbildung) - _A Anfangslage des Alterswertes - t _s Zeitintervall zwischen zwei Abtastungen - t Zeitintervall zwischen zwei Produktbildungen - Kreisfrequenz von Wechselstrom und und -spannung - T Periode von Wechselstrom und und -spannung - , Anfangsphasenwinkel - w Wert der Abtastung nach Gl. (13) - n _P3 Zahl der Produktbildungen in einer Tripelperiode - n _P2 Zahl der Produktbildungen in einer Tupelperiode - n _P1 Zahl der Produktbildungen in einer Singelperiode - a, b Zähler und Nenner eines Quotienten in teilerfremder Schreibweise - R _x Faktor vonb (der Indexx, z. B.x=12, gibt an, welchen Nennern der Faktor gemeinsam ist) - D _(n) Wertetripel}der nProduktbildung - Z _(n) Wertetripel}der nProduktbildung - Schwankungsbereiche Indices 1 erstes abgetastetes Signal (z. B. Wechselspannung) - 2 zweites abgetastetes Signal (z. B. Wechselstrom) - 3 Produktbildung - n laufender Zähler der Produktbildungen - i, j, i, j Summationsindices bei Abzählung vonn in geänderterReihenfolge Teil 2. Arch. Elektrotech. 68 (1985) 409–414     

Theorie der Raumladungs-Sperrschicht einer Niederdruckentladung zur Verwendung für eine Theorie der Rückzündung

Zusammenfassung Im ersten Teil der Arbeit wird die Theorie über die Raumladungs-Sperrschicht an der Grenze zwischen einem Niederdruck-Plasma und einer negativen Elektrode ausführlich dargestellt. Auf Grund des Boydschen Schichtkriteriums wird über die Ergebnisse von Bohm hinausgehend eine neue Randbedingung allgemein für die positive Säule im Bereich der ambipolaren Diffusion aufgestellt. Die Gültigkeit dieser Randbedingung wird an früheren Sondenmessungen von Klarfeld geprüft und bestätigt gefunden. Mittels der neuen Randbedingung wird in Verbindung mit früheren Messungen die Beweglichkeit der Quecksilber-Ionen bestimmt, die sich, bezogen aufp=1, als allein von der Elektronentemperatur abhängig erweist. Diese Ergebnisse werden bei der Betrachtung der Entionisierung des Gitter-Anodenraumes und des Ionenrückstromes zur Anode verwendet. Der Entionisierungsvorgang wird bei vereinfachter Anodensystemgeometrie sowohl statisch (mit Vernachlässigung der Sperrschicht vor der Anode) als auch dynamisch mit Berücksichtigung der Sperrschicht betrachtet. Es werden Meßergebnisse wiedergegeben und Übereinstimmung der Theorie mit der Erfahrung gefunden. Der von Koch angegebene Ansatz für den dynamischen Ionenrückstrom wird erweitert, womit die von Zipfel gemessenen hohen dynamischen Rückströme erklärt werden können. Es ergibt sich sowohl theoretisch als auch auf Grund einer dargestellten Sondenmeßmethode, daß die gemessenen Anodenrückströme bis zu sehr hohen Steilheiten der anlaufenden Sprungspannung (du /dt) praktisch reine Ionenströme sind.Übersicht der verwendeten Symbole A Konstante der Feldemissionsgleichung definiert durch Gl. (64) - a Korrekturgröße definiert durch Gl. (75) - B Konstante der Feldemissionsgleichung definiert durch Gl. (64) - b _i Beweglichkeit der Hg-Ionen;b _i1=b_ip - C wird mehrmals als Konstante verwendet - C ₁ - C ₂ - D Dimensionslose Größe, DurchschlagsbedingungD1 - D _a Ambipolare Diffusionskonstante für Hg,D _a1=D_a·p - d Abstand, Gitter-Anode - E Elektrische Feldstärke, an der AnodeE ₀, im Plasma an der Grenze zur SperrschichtE - e Elementarladung,e=1,602·10^–19 As - F _eff effektive Anodenoberfläche - J ₀,J ₁ Besselfunktion o. Ordnung und 1. Ordnung - i Anodenstrom - i _R Anodenrückstrom, ^: Spitzenwert, Index stat: statisch, Index dyn: dynamisch - j Stromdichte, ^: Spitzenwert, IndexV: Verschiebungsstromdichte - j ⁺ Ionenstromdichte zur Anode, ^: Spitzenwert. Bedeutung der Indizes:stat, statisch;dyn, dynamisch;K, Konvektion;P, vom Plasma;S, in der Sperrschicht erzeugt - j ⁺ Ionenwandstromdichte - j ^– Elektronenstromdichte, IndexF, in einem Feldemissionszentrum der Anode - k Boltzmann-Konstantek=1,38·10^–23 VAs/grad - l wird mehrmals als Längenmaß verwendet - M Masse eines Hg-IonsM=3,33·10^–25 kg - m Masse eines Elektronsm=9,106·10^–31 kg - m _F Feldverstärkungsfaktor Gl. (61) - n Neutralgasdichte; Index o, vor der Anode beit=0; Index 1, fürp=1,n ₁=3,54×10²² Atome je m³ und Torr - n _i, n_e Ionen- und Elektronendichte;n _e0, in der Symmetrie-Mitte des Plasmas;n _e, an der Plasmagrenze - p auf 0 °C reduzierter Druck,p=n/n ₁ - mittlerer Ionisierungsquerschnitt innerhalb der Schicht Gl. (71) - mittlerer Umladequerschnitt innerhalb der Schicht Gl. (79) - R Gefäßradius; Gitter- bzw. Blendenlochradius - r Zylinderkoordinate - S definiert durch Gl. (3) - T Zeitkonstante des gemessenen Rückstromes - T ₀ Zeitbereich für die Wahrscheinlichkeit Gl. (85) - T _A Temperatur der Anode - t Zeit - t Zeitdauer bis die Sperrschicht eine Sonde vor der Anode erreicht - U _e Elektronentemperatur, 11600 °K entsprechen 1 V - u Potential;u , Potentialdifferenz an der Sperrschichtu ^* , beim Spitzenwert des Rückstromesu _spr, Sprungspannung (Anode-Kathode) - u Anfangsgeschwindigkeit der Ionen an der Sperrschicht in Volt - Koordinate - - Korrekturgröße definiert durch Gl. (22) - Koeffizient der Elektronenemission durch auftreffende Ionen - Sperrschichtdicke, ₀ definiert durch Gl. (22) - ₀= 8.86 · 10^-12 As/Vm - - _i , definiert in Gl. (13) und Spreizfaktor siehe Gl. (73) - ₁ 1. Nullstelle der FunktionJ ₀, ₁=2,405 - Faktor für die dynamische Rückstromdichte Gl. (39) - Wandkorrekturfaktor für die Ladungsträgerdichte Gl. (1) - _i Raumladungsdichte in der Sperrschicht - definiert in Gl. (73) Die Ergebnisse der vorliegenden Arbeit werden in der im Arch. f. Elektrotechnik 49 (1964), H. 4, erscheinenden Theorie der Rückzündung bei Quecksilberdampf-Stromrichtergefäßen angewendet.     

The C-neu mammary carcinoma in Oncomice; characterization and monitoring response to treatment with herceptin by magnetic resonance methods

To characterize spontaneously occurring c-neu/HER2 overexpressing tumours in oncomice and their response to herceptin by non-invasive magnetic resonance spectroscopy (MRS) and magnetic resonance imaging (MRI). Oncomice were monitored by localized ³¹P MRS during unperturbed growth and before and after treatment with 10 mg/kg herceptin (Hoffman La Roche) intraperitoneally for up to 21 days post-treatment. Vascular morphology and function was assessed by quantitation of tumour magnetic resonance (MR) relaxation rates R₂* and R₂ prior to and either during carbogen (95% O₂/5% CO₂) breathing or following administration of the blood-pool contrast agent NC100150 (Clariscan, Amersham Health). Immunohistochemistry showed strong membrane staining for HER2 protein overexpression. The ³¹P MRS showed only a significant (p<0.01) increase of phosphomonoester / total phosphate ratio over 21 days of growth. Herceptin increased the tumour volume doubling time compared to untreated tumours and significantly increased the phosphomonoester / -nucleoside triphosphate ratio 2 days after treatment (p=0.01). Tumours showed a highly heterogeneous yet significant (p<0.01) decrease or increase in R₂* in response to carbogen or NC100150 respectively. The absence of a decline in tumour bioenergetics with growth, commonly seen in ³¹P MRS studies of transplanted rodent tumour models, coupled with the heterogeneous blood volume revealed by ¹H MRI, suggest a metabolic and vascular phenotype similar to that found in human tumours.     

Two-dimensional cylindrical model of the sector motor with a solid rotor

Contents In the paper, the Bubnov-Galerkin method coupled with the separation of variables was used to determine the electromagnetic field distribution. The field was assumed to be two-dimensional. On the basis of the calculations obtained the torque-slip characteristics of the sector motor were determined. The results were compared with the data presented in the literature of the subject.

---

Das zweidimensionale zylindrische Modell eines Sektormotors mit einem massiven Rotor

Übersicht Zur Ermittlung der Verteilung vom elektromagnetischen Feld im betrachteten Modell hat man die Bubnov-Galerkin-Methode in Verbindung mit der Methode der Variablentrennung angewandt. Man hat dabei angenommen, daß dieses Feld zweidimensional ist. Unter Verwendung der berechneten Feldverteilung hat man auch die mechanischen Kennlinien des Sektormotors ermittelt, sowie die erhaltenen Ergebnisse mit den in der Literatur zutrittlichen Daten verglichen.

---

List of symbols A vector potential, actual value - A vector potential (complex r.m.s. value) - A vector potential component with respect to thez-axis (complex r.m.s. value) - B _r ,B components of the magnetic induction vector in the cylindrical coordinates (complex r.m.s. values) - F force vector, actual value - F _a mean value of the vectorF - I r.m.s. value of the phase current per phase, layer and a pair of poles - imaginary unit - J current density vector (complex r.m.s. value) - J exciting specific electric loading (complex r.m.s. value) - J _n (u) Bessel function,n-th order, 1 st kind - k _c Carter coefficient taking into account the stator grooves - M _n mean torque for then-th harmonic - p number of the pairs of poles in the stator winding - |u| module of the complex number - z number of turns per phase, layer and a pair of poles - Re(u), Im(u) real and imaginary part of the complex numberu - derivative in the normal external direction - included angle taken by the specific electric loading of the stator - _Fe total included angle of the stator - ₀ magnetic permeability of vacuum - _Fe magnetic permeability of the rotor - conductivity - pulsation - _r angular velocity of the rotor - n _s synchronous rotational speed